Micro-Columnar CsBr:Eu Storage Phosphor for High-Efficiency High Energy Photon Radiography Panels

Eu-doped CsBr films (CsBr:Eu) exhibit excellent sensitivity for X-rays and are superior storage phosphors for high energy (MeV) photon radiography applications when coupled with thick copper or tungsten substrates. We report on the growth of micro-columnar CsBr:Eu films on copper substrates for megavolt (MV) X-ray imaging applications. Our films exhibit dense uniformly distributed micro-columns with an average diameter of $\sim 10~\mu $ m and a sharp, needle-like top. The advantage of this micro-columnar structured film is that the light can be channeled through the narrow columns to improve both light transmission and spatial resolution. We also determined the optimal Eu concentration in CsBr for the best storage phosphor performance. Growth of uniformly thick, micro-columnar structured films up to 2 mm was achieved on $2^{\prime \prime } \times 2^{\prime \prime }$ metallic substrates, which were then characterized by optically-stimulated luminescence (OSL) coupled with X-ray excitation. Furthermore, 5 mm thick film growth demonstrates the potential to scale up to even thicker films.